Saxitoxin and its structural analog neosaxitoxin were identified and quantified in mussels and sea stars that were collected from the Puget Sound region during harmful algal blooms. The analysis was based on high performance liquid chromatography with fluorescence detection and pre-column oxidation. Quantitative analytical results revealed that saxitoxin and neosaxitoxin were present in some of the Puget Sound samples well above toxic levels (up to 265 μg saxitoxin/100 g tissue and 111 μg neosaxitoxin/100 g tissue). For all of the samples of interest, paralytic shellfish toxins other than saxitoxin and neosaxitoxin were semi-quantified and a total toxicity value was estimated for each sample. The samples ranged from nontoxic to very toxic (up to 3687 μg saxitoxin-equivalents/100 g tissue).